Circuit controller



Nov. 5, 1935. N. c. SCHELLENGER 2,019,999

i CIRCUIT CONTROLLER original Filed Feb. 25, 1931 l aucune lUV. D, 1555 2,019,999 omovrr coNTaoLLEa Newton C. Schellenger, Elkhart, Ind., assigner to Chicago Telephone Srpply Company, Elkhart,

., a corporation of Indiana original application February z5, 1931, sel-m No.

518,281. Divided and this application March 31, 1932, serial Nn. 602,362

6Claims.

'I'his invention relates to circuit controllers, and is more particularly directed to the resistance strips employed in connection with such controllers.

'I'he present applicationis a division-of my copending application, Serial No. 518,281, led February 25, 1931, and in its preferred embodiment. is directed to the type of variable resistor comprising a resistance wire wound uponja flat strip or bar of insulating material, commonly referred to as the resistance strip, which strip is brought to a cylindrical shape substantially concentric with a shaft upon which a contact arm is aiiixed, the individual turns of the resistance strip being" progressively engaged by carried by the arm.

.The resistance of the present invention is adapted to be engaged along the iiattened surface of the strip, the contact of a turn of wire lying in means of thecontact shoe practice.

I have found that the coils of the resistance wire along the wide cylindrical surfaces adjacent the edgesof the resistance strip are held securely and are more nearlyuniform in height and spacing than those on the edge of the strip'. The strip may also be held without altering the uniformity of the winding on the inn'er cylindrical surface, which is engaged by the contacting means.

One object oi' the present invention is to prov ide a resistance strip which may include several vwires having different current conducting capacities, the relative length of each wire being varied as desired. By the use of wires of varying resistance characteristics, it is possible to gain an increased flexibility of resistance gradients. In connection with this feature, the application is particularly directed to the manner of providing connection between the respectively adjacent coils of the different resistance wires in order to eilect a permanent electrical connection therebetween, and to provide a smooth and graduated resistance change by means of the contacting shoe engaging the resistance strip.

The present invention is further characterisedl by the provision of a novel insulating strip for winding the resistance wire thereon, this strip being constructed preferably from insulating fibre, phenolic condensation products, or the like, and is preferably formed as a laminated structure, which, when heated, may be drawn into an arcuate or cylindrical shape in order to dispose it concentrically with respect to the contacting means.

being along the .lengththe plane of the strip, and not alcng theedge of the strip, as is the usualin a cylindrical configuration l The stripis formed as a at,elongated rectangular member, which has its edges preferably carefully rounded and truedso as to .assist in the accurate placing of the individual turns of the wire.

` Preferably, the strip is provided with spaced 5 grooves along its edges, and the resistance wire is placed in thesey grooves when wound upon the strip in order to provide accurate spacing between L the respective turns of the wire.

'I'he grooves formed on the edge of thestrip may be, relativev to the diameter of the wire, quite deep, and wire turns along the central part of the flat side of the strip may be secured in position by depositing a suitable cement along the center, of each side of the wound strip. 'Ihis cement is applied after the winding of the wire upon'the strip, and upon setting or hardening, the cement forms a definite tie between the central parts of the coil and the side of the strip, which serves to anchor the turns against any lateral shifting when engaged by the contactor, This :cement is preferably a. dense cellulosecement and possesses great strength, but is not brittle., upon setting.l Bending of the strip into arcuate form does not cause the cement to crack or the coils.

' If desired, the strip may not be provided with grooves at the edgesv thereof, but in such cases,

I prefer also to provide a line or band of cement along each edge, in order to assure that the wire 30 is wound upon the strip and is anchored against any' possibility of lateral shifting.

Another feature of the present invention is tho provision of la lresistance strip which may be Wound with wire of different diameters at different points along the lineal extent thereof, which are joined for effecting a smooth and positive/engagement of the contacting means therewith. This engagement is particularly achieved when the resistance strip is used in connection with the contacting means described in my abovementioned copending application. 'I'he windings are joined or bonded to each other by the use of a small piece of soft metal-foil, which is provided at the junction of th'e windings, and which bridges a suillciently large number of the turns to make a. good connection.

The method of bonding disclosed in the present invention is distinctly advantageous in connection with this type oi resistance strip. This comprises placing a small piece of lead wire over the point of juncture, and then pressing the wire or foil into engagement with the wires and embedding them in the foil. 'Ihis may be accomplished either manually or automatically. In

split from between 25.

manual operation, the foil is rst threaded under adjacent turns of the winding, and then the upper portion is looped over the underlying portion and pressed into position.

Another feature embodied in the resistance strip of the present invention is the particular construction provided at the terminal ends of the strip, whereby a large number of the turns adjacent each of the ends of the strip are shortcircuited, as by means of metal foil or the like, in order to provide a good contacting engagement with the base of the'terminal member positioned thereabove. this construction being such that no change of resistance can be' effected until after the contacting means has left the portion of the resistance strip lying under the terminal member.

Numerous other objects and advantages of the present invention will appear more fully from the following detailed description, which, taken in connection with the accompanying drawing, will disclose to those skilled inthe art the particular construction, and method of securing the features set out above.

In the drawing: C

v Figure 1 is a rear elevational view of a resisiance strip embodying one feature of my inven- Figure 2 is an elevational view of a resistance strip provided `with a terminal member for connectlng the strip to an external circuit:

Figure 3 is an elevational view of a strip embodying several features of the invention;

Figure 4 is a fragmentary diagrammatic sectional view, taken substantially on the line 4-4 of- Fig. 1 and showing the methodof joining adjacent turns of. two different kinds of wire for providing a junction therebetween;

Figure 5 is a fragmentary sectional view taken substantially on the line 5-5 of Figure 3, and showing a diil'erent method of performing the same connecting operation;

Figure 6 is an enlarged fragmentary detailed sectional view showing the terminal assembly disclosed in Figure 2; l

Figure 'I is an enlarged fragmentary detail view of the resistance strip, disclosing the grooves formed in the edges thereof for securing the turned wire in spaced relation; and

Figure 8 is a sectional view taken substantially 0n the line 8 8 of Figure 2.

Referring now in more detail tothe drawing, in Figure 1 I have disclosed an insulating member, indicated at 5, which is preferably composed of a strip of laminated phenolic compound of a special Icomposition, which renders the same sumciently flexible to permitbending when hot of the relatively short length which is employed into cylindrical shape, in order to accommodate the resistance within a cup-shaped housing.

The strip 5 may be formed from any vsuitable insulating material, such as fibre or the likerif desired. The edges C and 1 of the strip are preferably rounded, and are trued with respect to each other to provide parallel surfalc'es. The ends of the strip 5 are preferably notched, as indicated at 8, for accommodating a rivet or other suitable securing means when the strip is bent into cylindrical form, for securing the resistance strip in fixed position. within the housing of the rheostat. The particular manner of securing the resistance strip, by means of the notches formed in the abutting edges thereof, is described in detail in my copending application, Serial No. 518,281,

lfilled February 25, 1931.

Upon the strip 5 is preferably Wound a resistance wire, indicated at 9, which is of relatively small diameter, for example, .002 of an inch, and which extends along `the strip for a substantial length thereof.l The wirevis bare, and is spaced approximately .0001 of an inch between turns, which provides for approximately 466 turns per lineal inch. Of course, these dimensions may be varied greatly without departing from the invention disclosed. From the opposite end of the strip 5, a second resistance wire III is wound about the strip, this wire possessing diierent current carrying characteristics than the wire 9, and may, orrmay not be, of the same diameter. The two windings 9 and I0 meet at a point adjacent that indicated by the reference numeral II, and are suitably connected together by means of the metal foil member I2.

Referring now in detail to Figure 4, which illustrates one method of connecting the windings l and I I), I have disclosed therein a strip of 20 metal foil I2, which is preferably of soft metal, such as lead or the like, the strip having one end thereof threaded, as by means of a needle or the like, under the adjacent pairs of turns of the windings 9 and III. This portion of the 25 metal foil is indicated by the numeral I3. After the portion I3 has been inserted under the respective pairs of turns of the windings 9 and III, the remaining portion of the foil member I2 is bent over, as indicated in dotted lines in Figure 4, and engages the upper surfaces of the windings. Suitable pressure may Vthen be applied, either by means of a press, or by means of the compressive expansion of the resistance strip within the housing by means of the securing rivet, as described in my copending application, for pressing the metal foil member rmly'about the turns of the windings, in order that good electrical contact may be made therebetween. The foil member, being made of relatively soft metal, is easily 40 pressed downwardly so as' to fill up the interstices between the adjacent turns of the windings and to aiford a'compact and effective connecting means.

Considering 4now Figure 2, it will be noted that i5 the resistance strip is similar to the resistance strip 5 of Figure 1, and has been correspondingly identified. In vorder to assure that the winding of the resistance wire will be accurately held iii spaced relationship upon the resistance 50 strip during movement of the contacting means, I preferably provide .a band of cement, indicated by the numeral Il, alongvthe central part of the fiat side of the strip. If desired, similar bands of cement I5 and I6 may be vprovided along the 55 edges 5 and 1 of the strip for further assuring that the individual turns of the resistance wire will be held in proper spac'ed relationship. Preferably bare wire is employed, as with the method of making contact disclosed in my copending application, bare wire with very little space between the respective turns thereof is entirely feasible, and there is not the dilculty of removing the enamel, or other insulation, which is the case in rheostats where enameled wire or the like is employed. The cement used for providingthe bands Il, I5 and I6, is preferably a tough, dense cellulose cement that possesses great binding strength, but does not become brittle upon hardening. Thus,bending of the Astrip 5 into 70 arcuate form after winding will not cause the cement to crack or split from between the coils of the winding.

Considering now the left hand end of the strip 5 of Figure 2, it will be noted that a plurality 75 tion with the` turns Il either by hand or by a- V*machine press.

of the individual tums il of the resistance wire woundupon the strip are covered by a soft metal Vfoil member IB', which, as shown more clearly in Figures 6 and 8, is pressed down about each of vthe turns I1 of thc winding, and completely fills the spaces between adjacent turns. 'Ihis foil member 18 may be pressed into engaging rela- Disposed in contacting relation with the foil member I8 is the terminal member 20, which is provided with the lead portion 2l, and with the cut-out portion 22 fitting about the notch 8 in the resistance strip 5. lThis terminal member is described in detail in myy copending application, Serial No. 602,007, filed March 30, 1932.

In the embodiment shownin Figure 3, I have provided a resistance strip 5 which has wound thereon three different resistance wires, these wires being indicated, respectively, by the numerals y23, 24, and 25. The resistance wire 25 is of substantial diameter, as compared to the wires 2-3 land 24, and provides for relatively small change inv resistance per unit of length with The junction of respect tothe other two wires. the wires 23 and 24, and the wires 24 and 25, is similar to that described in connection with Figure 1. but, in the present embodiment, the metal. foil members 26 and 21 are not placed in position manually, as described in connection with Figure 4, but are pressed into contact en- Gazing relation between the respective turns of Athe different windings by means of a machine operated press. y

Considering in detail Figure 5, I have shown the resistance strip 5 disposed below the feeding mechanism of a machine press. A suitable upper bed portion 28 is adapted to rest upon the upper surface of the resistance strip 5,-andy is provided with a cut-out portion adapted to receive the ram or punch 29. A suitable soft metal wire, indicated at 30, is fed through the slot 3| ,into the cut-out portion in which the ram 29 operates, and is sheared off by downward movement of the ram to-a length corresponding to the width of the cut-out portion'. The ram 29 then forces the'soft metal foil strip 21 downwardly into contact engaging relation with the windings 24 and 25, and serves to press themetal around the adjacent peripheries -of each of' the windings, thus forming' an effective electrical contact therebetween.

It will be noted in Figure 3 that I have-pro- -vided a relatively 'wide band of cement, indi-l cated by the numeral 32, along the central portion of the flat side'of the resistance strip 5, and have provided relatively `narrow portions or bands of a cement along the edges of the strip.

'Ihis is similar to the disposition of the cement shown in Figure 2.

In 'the enlarged view of the strip shown in Figure' 7, the cement is omitted from the edges of the strip, and in place thereof the edges are provided with spaced grooves 35, these grooves l5 being adapted to receive the individual turns I6 of the resistance wire winding. If desired. cement may also be applied to the wire winding engaging in the grooves '35, after the strip has been wound, but I have found that this is unL necessary when the-parallel extending edges of the. strip are provided with grooves for receiving the wire, since thegrooves serve to space the wire a denite distance between the respective I' turns thereof, and also hold the wire in proper spaced relationship. As shown in more detail in Figure 8, the edges of the insulator strip 5 are rounded, in order to present no sharp corners to the wire being wound thereon.

It is apparent that the wire may be held in spaced relation along the strip by means of either 5 cement, disposed along the fiat surface of the strip and the extending parallel edges thereof, or by means of spaced grooves formed in the edges, or both means may be employed if desired. Also, the strip may be wound having wire of varying l0 sizes, and with varying current. 4carrying characteristics, in order to increase the iiexibility-of resistance gradients, the method of interconnccting the adjacent turns of two types of wire being applicable to either situation. Also, the 1.5 composition of the strip, together with the cementing means used in connection with the winding, permits the strips to be bent into cylindrical form without danger of impairing the spaced relation between adjacent turns of the winding. .Since bare wire is employed in this resistance strip, it is imperative that this spaced relationship be maintained, and to this end I have provided a resistance strip which may be either grooved and supplied with a cementitious material, or with a plurality of bands of cementitious material, in order 'to maintain the required spaced relationship between the individual turns of the windings.

I do not intend to be limited to the exact `de- 30 tails shown and described in the illustrated embodiment of my invention, but only in so far as defined by the scope. and spirit of the appended claims.

I claim: 35

l. The method of forming a combination r- Sistor and terminal which comprises winding a resistance wire on an insulating support, pressing a soft metal pad around and between. the end turns of said winding and mounting a ter- 40 minal in abutting relation with vsaid soft metal pad.

2. In the method of forming a combined resistor and terminal of the type having a wind--v ing and a terminal electrically connected thereto, the. steps which comprise winding a resistance wire on an insulating support, disposing a soft metal pad in Contact with the end turns of the winding, pressing the metal constituting said pad to cause the metal to flow between and around the end turns-of said Winding, flattening the top surface of said pad, and seating a terminal element on the flattened top surface of the pad.

. 3. In combination, an insulating support, a wire coil wound thereabout, a terminal member, and means for establishing connection between said terminal member and a plurality of turns of said coil adjacent an end thereof comprising la sheet of conducting material extruded into engagement with said turns whereby the turns are 00 embedded in the conducting material, said terof conducting material extruded into engagement "(0 with said turns whereby the turns are embedded inthe conducting material, said base portion of said terminal member engaging the face of said material.

5. The method of making a combined resistor and terminal which comprises winding a resistance wire on a fiat strip of insulating material,`

disposing a soft metal pad Iadjacent the end turns of the winding thus formed, pressing the pad to effect a cold ow of the material of the pad between said end turns to embed the end turns in said pad and thus secure the end of said coil while maintaining the outer surface of said pad substantially smooth, and disposing a terminal on the smooth, outer surface of said pad in intimate contact therewith.

6, In combination with aresistance strip having a plurality of turns of resistance/wire positioned around a insulating support, asoit metal pad pressed into engagement with and between fthe end turns of said resistance wire, said soft metal pad provided with a substantially smooth, outer surface, and a terminal having a substantially smooth-faced base portion thereof in con- -tact with the outer surface of said pad.

n, NEWTON C. SCI-IEILENGER. l0 

